The Division of Nephrology of Duke University Medical Centers applying to participate in phases III and IV of the Cooperative Clinical Study of Dietary Modification on the Course of Progressive Renal Disease (MDRD study). The MDRD Study has the three-fold objectives of testing the effectiveness, safety, and acceptability of dietary modifications of protein and phosphate in patients with reductions in glomerular filtration rate from renal diseases of various etiologies. The research protocols have been deigned and tested by the NIH during the planning and feasibility phases. Additional centers are new sought to assure a statistically valid number of patients and to broaden the geographic representation. The present proposal could enroll patients from the piedmont area of North Carolina and contiguous state with primary sources being the patient populations served by the Duke University and the Durham Veterans' administration medical centers and their referring physicians. Major strategies are outlined to assure enrollment of 40-50 eligible subjects. These strategies are based in part on recent experience in enrolling large numbers of patients in clinical studies involving hypertension. The study would use the Duke University Clinical research Unit outpatient facilities with major attention to the critical role of the study dieticians in implementing the treatment program.